sw to produce a swept interrogation light signal, launching the swept interrogation light signal into the sensor array, detecting reflected signals being returned from the sensor array by each of the reflectors, respectively, wherein detection includes mixing a return light signal from the sensor array with a local oscillator signal onto an optical receiver to produce an electrical radio frequency signal, demultiplexing the electrical radio frequency signal into a first signal channel and a second signal channel, corresponding to the first and second reflector, respectively, demodulating each of the first and second signal channel into a first phase response from the first reflector and a second phase response from the second reflector, and subtracting the first phase response from the second phase response to obtain a sensor phase signal.
G01D 5/26 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette
2.
Processing data from a distributed fibre-optic interferometric sensor system
A method of processing data from a distributed fibre-optic interferometric sensor system for measuring a measurand, the system comprising multiple interferometric sensors. The method comprises interrogating two or more of the multiple interferometric sensors to record a raw measurement time series for each of the sensors. The method further comprises calculating a common reference time series as a measure of central tendency of the raw measurement time series from two or more reference sensors, the reference sensors being selected from the multiple interferometric sensors. Finally, the method comprises compensating at least one raw measurement time series from a measurement sensor selected from the multiple interferometric sensors with the common reference time series to produce a compensated measurement time series, the measurement sensor being configured to be sensitive to the measurand. The invention further relates to a distributed fibre-optic interferometric sensor system.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
The invention relates to a hydrophone housing. The housing comprises an outer casing with an exterior shape being in close contact with sediment when buried therein and having a deflectable wall part. Solid material partly fills the casing to define an outer chamber behind the deflectable wall part, a cavity shaped so that an inner chamber is defined immediately surrounding a hydrophone sensing element held therein, and a first duct for liquid flow communication between the outer chamber and the cavity or an internal volume of the hydrophone sensing element. Thereby, a hydraulic coupling is provided so that an acoustic pressure causing small radial displacements of outer surface of the housing will, via liquid in the first duct, cause large radial displacements of the hydrophone sensitive element. The area of the deflectable wall part is much larger than the area of the sensitive element so that only small displacements of the housing are required to cause large displacements at the hydrophone sensing element.
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
Methods and apparatus for cable termination and sensor integration at a sensor station within an ocean bottom seismic (OBS) cable array are disclosed. The sensor stations include a housing for various sensor components. Additionally, the sensor stations can accommodate an excess length of any data transmission members which may not be cut at the sensor station while enabling connection of one or more cut data transmission members with the sensor components. The sensor stations further manage any strength elements of the cable array.
There is provided a solid seismic streamer cable for use in seismic surveying in marine environments. The streamer is characterized by a buffer layer 2 which is provided with a cut-out 50 and a sensor element arranged in the cut-out 50. There is also provided an associated hydrophone for integration into the seismic streamer cable. The hydrophone is characteristic in a split-element sensor base 10, 11 being suited for efficient mounting into the cut-outs 50 of the seismic cable. There is also provided an associated accelerometer for integration into the seismic streamer cable. The accelerometer is characteristic by a split-element sensor base 30, 35 for being efficiently arranged into the cut-outs 50 of the seismic cable. A method of producing a seismic streamer cable according to the invention incorporating a hydrophone or accelerometer according to the invention is also provided.
H01R 43/00 - Appareils ou procédés spécialement adaptés à la fabrication, l'assemblage, l'entretien ou la réparation de connecteurs de lignes ou de collecteurs de courant ou pour relier les conducteurs électriques
G01V 13/00 - Fabrication, étalonnage, nettoyage ou réparation des instruments ou dispositifs couverts par les groupes
G01P 15/093 - Mesure de l'accélération; Mesure de la décélération; Mesure des chocs, c. à d. d'une variation brusque de l'accélération en ayant recours aux forces d'inertie avec conversion en valeurs électriques ou magnétiques au moyen de capteurs photo-électriques
B spool. Correspondingly, a method for ensuring a continuous connection between two items 30,40 that rotates with respect to each other is provided. The method comprises arranging a rotary joint or swivel device according to any of the embodiments of the invention between the two items.
B66F 3/00 - Dispositifs, p.ex. crics, adaptés pour lever des charges d'un mouvement continu
H02G 1/10 - Méthodes ou appareils spécialement adaptés à l'installation, entretien, réparation, ou démontage des câbles ou lignes électriques pour poser les câbles, p.ex. appareils de pose sur véhicule dans ou sur l'eau
H02G 11/00 - Installations de câbles ou de lignes électriques entre deux pièces en mouvement relatif
A subsea installation tool for installing a flexible body, e.g. a subsea fiber cable on a seabed from a surface vessel, and an associated method for installing the flexible body on the seabed is provided. The installation tool includes a tensioner that may be coupled to the flexible body to actively pull it down, thus increasing tension in an upper section of the cable from the installation vessel to the installation tool. High tension in the upper part of the cable gives good control even in strong sea currents. At the same time the tensioner enables lower tension in the bottom part cable from the installation tool to the seabed, giving good control of the touchdown position on the seabed.
H02G 1/10 - Méthodes ou appareils spécialement adaptés à l'installation, entretien, réparation, ou démontage des câbles ou lignes électriques pour poser les câbles, p.ex. appareils de pose sur véhicule dans ou sur l'eau
G02B 6/50 - Installation souterraine ou sous l'eau; Installation à travers des tubes, des conduits ou des canalisations
H02G 9/02 - Installations de lignes ou de câbles électriques dans ou sur la terre ou sur l'eau tendus directement dans ou sur le sol, lit de rivière ou fond de mer; Leur recouvrement, p.ex. tuiles
Methods and apparatus for cable termination and sensor integration at a sensor station within an ocean bottom seismic (OBS) cable array are disclosed. The sensor stations include a housing for various sensor components. Additionally, the sensor stations can accommodate an excess length of any data transmission members which may not be cut at the sensor station while enabling connection of one or more cut data transmission members with the sensor components. The sensor stations further manage any strength elements of the cable array.
G01V 1/38 - Séismologie; Prospection ou détection sismique ou acoustique spécialement adaptées aux zones recouvertes d'eau
G01V 1/16 - Séismologie; Prospection ou détection sismique ou acoustique Éléments récepteurs de signaux sismiques; Aménagements ou adaptations des éléments récepteurs
G02B 6/44 - Structures mécaniques pour assurer la résistance à la traction et la protection externe des fibres, p.ex. câbles de transmission optique
9.
Fibre optic accelerometer and a method of manufacturing a fibre optic accelerometer
A tri-axis accelerometer for use in seismic surveying is provided. The accelerometer comprises at least three fiber optic accelerometer elements which have respective fiber sensor coils, and which are characteristic in that the fiber sensor coils are coiled about a common coiling axis and at least one of the accelerometer elements is a slant angle accelerometer element. A corresponding method of manufacturing a tri-axis fiber optic accelerometer is also disclosed. A fiber optic tri-axis accelerometer for sensing acceleration in three directions is also provided, which comprises a first, a second, and a third sensor base, each base including a first, a second, and a third fixed element, respectively, and a first, a second, and a third movable element, respectively, each pair of fixed and movable elements carrying a fiber sensing coil. The fiber sensing coils are all coiled around a common coiling axis and at least one of the movable elements is designed and mounted so as to be movable in a direction that is slanted with respect to the common coiling axis.
G01P 15/08 - Mesure de l'accélération; Mesure de la décélération; Mesure des chocs, c. à d. d'une variation brusque de l'accélération en ayant recours aux forces d'inertie avec conversion en valeurs électriques ou magnétiques
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
There is provided a solid seismic streamer cable for use in seismic surveying in marine environments. The streamer is characterized by a buffer layer 2 which is provided with a cut-out 50 and a sensor element arranged in the cut-out 50. There is also provided an associated hydrophone for integration into the seismic streamer cable. The hydrophone is characteristic in a split-element sensor base 10, 11 being suited for efficient mounting into the cut-outs 50 of the seismic cable. There is also provided an associated accelerometer for integration into the seismic streamer cable. The accelerometer is characteristic by a split-element sensor base 30, 35 for being efficiently arranged into the cut-outs 50 of the seismic cable. A method of producing a seismic streamer cable according to the invention incorporating a hydrophone or accelerometer according to the invention is also provided.
G01V 1/38 - Séismologie; Prospection ou détection sismique ou acoustique spécialement adaptées aux zones recouvertes d'eau
G01V 13/00 - Fabrication, étalonnage, nettoyage ou réparation des instruments ou dispositifs couverts par les groupes
G01P 15/093 - Mesure de l'accélération; Mesure de la décélération; Mesure des chocs, c. à d. d'une variation brusque de l'accélération en ayant recours aux forces d'inertie avec conversion en valeurs électriques ou magnétiques au moyen de capteurs photo-électriques
Container systems used in storage, deployment or retrieval of a seismic cable array comprise a container, at least two coiling elements attached to a bottom side of the container, and storage means for allocating or accommodating, in an ordered arrangement, a number of seismic stations and/or a number of couplers/splices and/or other discontinuities which are being interconnected by sections of the seismic cable. Said storage means is arranged between said coiling elements and are attached to the bottom side of the container. The seismic cable is spooled or wound around said coiling elements. Corresponding methods of storing a seismic cable and deploying/retrieving the seismic cable are based on the use of at least two coiling elements and storage means for allocating or accommodating a number of seismic stations and/or a number of couplers/splices and/or a number of other discontinuities and arranged between said coiling elements.
Methods and apparatus for cable termination and sensor integration at a sensor station within an ocean bottom seismic (OBS) cable array are disclosed. The sensor stations include a housing for various sensor components. Additionally, the sensor stations can accommodate an excess length of any data transmission members which may not be cut at the sensor station while enabling connection of one or more cut data transmission members with the sensor components. The sensor stations further manage any strength elements of the cable array.
Methods and apparatus for interrogating optical sensors with high slew rates using non-uniform sampling are provided. The transmission of optical signals in a non-uniform pattern is employed to allow for demodulation of fringe rates exceeding the commonly understood Nyquist frequency limit given as one half of the mean sampling frequency. By monitoring the time dependent fringe frequency and assuming that the fringe frequency has a limited bandwidth, only a limited bandwidth smaller than the Nyquist bandwidth around the instantaneous fringe frequency needs to be reconstructed at any time.
A method and apparatus for demodulation of detected fringes from interferometric sensors with high slew rates are provided. A detected interference signal may be mixed with a local oscillator phasor to obtain a mixed signal, the local oscillator being controlled to produce a frequency that roughly matches the fringe frequency of the interference signal. A sensor phase estimate may be obtained from the detected interference signal or the mixed signal. The local oscillator signal can be computed from the sensor phase estimate. The mixed signal and the sensor phase estimate may be low pass filtered and decimated and the resulting decimated mixed signal and decimated sensor phase estimate may be processed and combined with moderate processing power requirements in an effort to accurately measure the sensor phase for the interferometric sensor.
Methods and apparatus for cable termination and sensor integration at a sensor station within an ocean bottom seismic (OBS) cable array are disclosed. The sensor stations include a housing for various sensor components. Additionally, the sensor stations can accommodate an excess length of any data transmission members which may not be cut at the sensor station while enabling connection of one or more cut data transmission members with the sensor components. The sensor stations further manage any strength elements of the cable array.
Seismic sensor systems and sensor station topologies, as well as corresponding cable and sensor station components, manufacturing and deployment techniques are provided. For some embodiments, networks of optical ocean bottom seismic (OBS) stations are provided, in which sensor stations are efficiently deployed in a modular fashion as series of array cable modules deployed along a multi-fiber cable.
A bend stiffener includes a first elongate member having a longitudinal conduit and a second elongate member also having a longitudinal conduit connected to an end of the first member thereby effectively extending the length of the bend stiffener. The first member has a resilience to bend when the bend stiffener is subject to a certain load, i.e. at a large tension and small angle, while the second member is designed to have less resilience than the first member, whereby the second member starts bending earlier than the first member when the bend stiffener is subjected to a smaller load, i.e. at a low tension and/or a large angle. The first and second members may provide one or more channels from the second member to the hydrophone. The channel surfaces may have a nonmetallic material. The second member has a resilience to transfer incident pressure waves into the channel therein.
Seismic sensor systems and sensor station topologies, as well as corresponding cable and sensor station components, manufacturing and deployment techniques are provided. For some embodiments, networks of optical ocean bottom seismic (OBS) stations are provided, in which sensor stations are efficiently deployed in a modular fashion as series of array cable modules deployed along a multi-fiber cable.
Seismic sensor systems and sensor station topologies, as well as corresponding cable and sensor station components, manufacturing and deployment techniques are provided. For some embodiments, networks of optical ocean bottom seismic (OBS) stations are provided, in which sensor stations are efficiently deployed in a modular fashion as series of array cable modules deployed along a multi-fiber cable.
Seismic sensor systems and sensor station topologies, as well as corresponding cable and sensor station components, manufacturing and deployment techniques are provided. For some embodiments, networks of optical ocean bottom seismic (OBS) stations are provided, in which sensor stations are efficiently deployed in a modular fashion as series of array cable modules deployed along a multi-fiber cable.
Seismic sensor systems and sensor station topologies, as well as corresponding cable and sensor station components, manufacturing and deployment techniques are provided. For some embodiments, networks of optical ocean bottom seismic (OBS) stations are provided, in which sensor stations are efficiently deployed in a modular fashion as series of array cable modules deployed along a multi-fiber cable.
Unwanted signal components in time-division multiplexed (TDM) systems may lead to crosstalk and noise if these pulses overlap with signal pulses from an interrogated sensor. The crosstalk and noise are dominated by interference between the signal pulses from the interrogated sensor and the unwanted signal components and can be greatly reduced by suppressing this interference signal. The unwanted signal components may include overlapping pulses originating from different sets of interrogation pulses (repetition periods). Modulating the phase or frequency between the repetition periods so that the unwanted interference signal does not appear at frequencies from which the phase of the interrogated sensor is demodulated suppresses this interference. Other unwanted signal components include leakage light during dark periods of the duty cycle of an interrogation signal. Modulating the phase difference between the interrogation signal and the leakage light suppresses the interference between the leakage light and the interrogation signal.
Seismic sensor systems and sensor station topologies, as well as corresponding cable and sensor station components, manufacturing and deployment techniques are provided. For some embodiments, networks of optical ocean bottom seismic (OBS) stations are provided, in which sensor stations are efficiently deployed in a modular fashion as series of array cable modules deployed along a multi-fiber cable.
A seismic sensor station includes a housing containing a fiber optic hydrophone and a fiber optic accelerometer that can both be made from a single length of optical fiber arranged inside the housing. The fiber optic accelerometer is arranged in a liquid/oil filled compartment of the housing for dampening of mechanical resonances in the accelerometer due to mechanical disturbances and pressure fluctuations.
G01V 8/24 - Détection, p.ex. en utilisant des barrières de lumière en utilisant plusieurs émetteurs ou récepteurs en utilisant des fibres optiques
G01V 8/16 - Détection, p.ex. en utilisant des barrières de lumière en utilisant un émetteur et un récepteur en utilisant des fibres optiques
G01V 1/38 - Séismologie; Prospection ou détection sismique ou acoustique spécialement adaptées aux zones recouvertes d'eau
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
Storage and installation systems used in storage, deployment or retrieval of a seismic cable array include one or more baskets adapted for being stacked. Each basket is dimensioned to allocate, in an ordered arrangement, a number of seismic stations interconnected by sections of seismic cable. Corresponding methods of storing a seismic cable and deploying/retrieving a seismic cable are based on the use of baskets having an ordered arrangement of seismic stations.
Methods and apparatus for cable termination and sensor integration at a sensor station within an ocean bottom seismic (OBS) cable array are disclosed. The sensor stations include a housing for various sensor components. Additionally, the sensor stations can accommodate an excess length of any data transmission members which may not be cut at the sensor station while enabling connection of one or more cut data transmission members with the sensor components. The sensor stations further manage any strength elements of the cable array.
Unwanted signal components in time-division multiplexed (TDM) systems may lead to crosstalk and noise if these pulses overlap with signal pulses from an interrogated sensor. The crosstalk and noise are dominated by interference between the signal pulses from the interrogated sensor and the unwanted signal components and can be greatly reduced by suppressing this interference signal. The unwanted signal components may include overlapping pulses originating from different sets of interrogation pulses (repetition periods). Modulating the phase or frequency between the repetition periods so that the unwanted interference signal does not appear at frequencies from which the phase of the interrogated sensor is demodulated suppresses this interference. Other unwanted signal components include leakage light during dark periods of the duty cycle of an interrogation signal. Modulating the phase difference between the interrogation signal and the leakage light suppresses the interference between the leakage light and the interrogation signal.
An optical wavelength readout system for application in optical sensing systems is disclosed. The system includes a Master unit including a wavelength swept optical source for launching light into a string of optical sensors, and a detection and processing unit for detecting and processing the light emitted by the source. The system also includes a Slave unit including a light coupling device for coupling light from the light source into the string of sensors and for coupling light reflected from the string of sensors to a detection and processing unit arranged to detect and process the reflected light. The Master unit includes a wavelength reference unit adapted to make a reference signal available to other parts of the sensing system. The reference signal represents a generally exact relation between the wavelength of the light emitted from the source and time.
An optical wavelength readout system for application in optical sensing systems is disclosed. The system includes a Master unit including a wavelength swept optical source for launching light into a string of optical sensors, and a detection and processing unit for detecting and processing the light emitted by the source. The system also includes a Slave unit including a light coupling device for coupling light from the light source into the string of sensors and for coupling light reflected from the string of sensors to a detection and processing unit arranged to detect and process the reflected light. The Master unit includes a wavelength reference unit adapted to make a reference signal available to other parts of the sensing system. The reference signal represents a generally exact relation between the wavelength of the light emitted from the source and time.
A method for interrogating time-multiplexed interferometric sensors using multiple interrogation pulses so as to increases the allowable interrogation pulse duty-cycle and improve the signal-to-noise ratio. In each TDM repetition period a sequence of multiple interrogation pulses are generated. The pulses in the sequence are separated by a time that is equal to the sensor imbalance. The phase from pulse to pulse in each TDM time-slot is modulated at a different, linear rate such that the pulse in time-slot m will have an optical frequency that is shifted by mΔν, where Δν is the sub-carrier frequency. Because multiple reflections do not need to fade out the inventive method can enhance the signal-to-noise ratio of interferometric sensors such as inline Fabry-Perot sensors.
Devices and methods of accurately determining optical wavelengths, such as the Bragg wavelengths of an FBG sensor array. Wavelength-swept light having a characteristic spectrum is swept over a bandwidth and is applied to an interference filter. The interference filter produces an optical spectrum having one or more reference peaks that are identifiable because of the characteristic spectrum. The optical spectrum is converted into electrical signals having at least one electrical signal that is identifiable because of the characteristic spectrum. The identifiable electrical signal is used by a signal processor as an absolute, high accuracy wavelength reference. Temperature compensation or temperature stabilization can compensate the characteristic wavelength. Fiber Bragg sensor systems can use the wavelength reference to determine the Bragg wavelength of FBG elements. The characteristic spectrum can be imparted by the light source or an optical element such as a transmission line filter.
Embodiments of the present invention generally provide methods, apparatus, and systems for compensating for frequency fluctuations in source light used to interrogate an optical sensor. The optical sensor may be interrogated to generate a sensor signal. A reference device co-located with the optical sensor may also be interrogated to generate a reference signal. Optical parameters extracted from the reference signal may be used to correct parameters extracted from a sensor signal.
Methods and apparatus reduce coherence of an optical signal that is used to interrogate optical interferometric sensors. The optical field phasor of the interrogation source is modulated in a controlled manner to produce a broadened optical source power spectrum at the output of the source unit. The output from the source unit is launched into an optical sensor network, comprising a multiple of optical pathways from its input to the detection unit, where pairs of optical pathways form sensor interferometers. A compensating interferometer with delay difference similar to the sensor delay difference may be arranged in a serially coupled manner with the optical sensor network, either before or after the network. The coherence modulation may be performed through direct modulation of the source or through external modulation of the light with piezoelectric ring modulator, a Lithium niobate phase or intensity modulator, or an acoustooptic modulator.
A method and apparatus for reducing crosstalk between sensors in an inline Fabry-Perot (FP) sensor array. The inline FP sensor array comprises a plurality of fiber Bragg gratings arranged periodically along an optical fiber. The sensors are formed between each of the Bragg gratings. A light source provides multiplexed pulses as interrogation pulses for the array. The light pulses are applied to one end of the sensor array and a light detector detects reflected pulses. The detected pulses comprise a composite of reflections from all the Bragg gratings along the fiber. The apparatus processes the detected signals using an inverse scattering algorithm to detect an accurate phase response from each of the Bragg sensors while reducing crosstalk from other Bragg sensors within the array. One form of inverse scattering algorithm is a layer-peeling algorithm.
A method and apparatus that uses specific source modulation and detectors to detect a response that carries information about a system response matrix associated with each sensor in a interferometric sensor array and extracting a sensor response in a manner that eliminates polarization-induced signal fading and that is insensitive to lead fiber birefringence fluctuations.
Fiber optic particle detector for measurements in a fluid flow, comprising an optical fiber (2,3,12) being acoustically coupled to a mechanical element (11,13,14) adapted to be acoustically coupled to the flow, a fiber optic interferometer (54,56) and a light source (12,51,55) providing light in said optical fiber.
brevets
